DE9407806U1 - Intervertebral implant - Google Patents

Description

A 51 969 u Applicant: AESCULAP AG

u-214 Am Aesculap-Platz

9 May 1994 78532 Tuttlingen

DESCRIPTION

INTERVERTEBRATE IMPLANT

The invention relates to an intervertebral implant with support surfaces that can be placed on adjacent vertebral bodies and with an adjustment device for changing the relative position of the support surfaces.

After the removal of intervertebral bodies, there is a risk that neighboring vertebral bodies will lie directly on top of one another and that this unnatural misalignment will cause damage to both the supporting apparatus and the surrounding soft tissue.

To avoid this, it is known to replace the intervertebral bodies after removal with an intervertebral implant, for example in the form of a cuboid or a wedge. Inserting such intervertebral bodies is difficult, so intervertebral bodies are often inserted that do not have the required size. If the intervertebral bodies are chosen to be slightly smaller,

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the implantation is easier, but the support function cannot be fully fulfilled.

It is already known to use intervertebral implants, the external structure of which can be changed after insertion using a suitable adjustment device. For example, WO 92/14423 describes an intervertebral implant with a tension rod, in which side wall sections arranged so as to be pivotable between adjacent front surfaces of the implant can be pivoted more or less outwards by a tension rod. Although this makes it possible to change the size of the intervertebral implant after implantation, the structure of such an intervertebral implant is extremely complicated and also does not allow the support surface to be placed flatly on the vertebral body, since the support surfaces have to be pivoted over a small area.

EP 260044B1 discloses a two-part intervertebral implant in which expansion bodies are arranged between two parts, which can also move the expansion surfaces away from each other using tension rods and axial displacement. Here too, the structure of the implant is relatively complicated, as a large number of parts are required. In addition, only a linear system is created here, as the outer surface of this implant has a circular cross-section.

A similar structure of an intervertebral implant is described in WO 90/00037. Wedge-shaped expansion elements between two support surfaces are brought more or less closer together by a tension rod and thereby press the

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Support surfaces apart. Here too, a large number of individual parts are required that must be assembled to form the intervertebral implant, so that the risk of functional disorders cannot be ruled out.

The object of the invention is to improve a generic intervertebral implant so that a particularly simple and robust structure and trouble-free function are guaranteed.

This object is achieved according to the invention in an intervertebral implant of the type described at the outset in that the support surfaces are formed by the outer sides of the legs of a U-shaped support body, which run essentially parallel to one another, in that a threaded hole is arranged in a web of the support body which connects the legs to one another in one piece, and in that a screw is screwed into this hole, which rests on the inner surfaces of the legs which approach one another towards the free end of the legs and thereby bends the legs outwards more or less depending on their screw-in depth.

In contrast to all other known intervertebral implants with adjustment options, a one-piece support body is used, into which only a screw is screwed as an adjustment device. This screw lies directly on the inner surfaces of the legs of the support body and pushes them apart more or less depending on the depth of the screwing. This intervertebral implant is extremely simple in design, as it only consists of two parts, and it still allows for very sensitive adjustment of the support surfaces.

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lein by bending the legs outwards. This slight pivoting of the support surfaces is also beneficial from an anatomical point of view, as it allows a slight lordosis of the vertebral bodies to be achieved, and this size can also be adjusted particularly easily using the screw. It is also possible to vary the amount of spreading by screwing different screws into the support body, in particular the absolute amount of adjustment that occurs per screw-in depth of the screw can also be adjusted.

A particular advantage of bending the legs is that it reliably prevents the implant from sliding in the dorsal direction, since the intervertebral space narrows in this direction and the implant is prevented from moving further in the dorsal direction due to its wedge shape.

It is advantageous if the screw tapers conically in its tip area, in this way a larger contact surface of the screw on the inner surface can be achieved and thus also less friction between the screw and the inner surface when screwing in. It is also advantageous if the screw is thread-free in its tip area.

Preferably, the screw rests on the inner surface of the legs in the front third, so that the legs are then supported by the web at the rear end and then by the screw in the area of the front end.

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It is advantageous if the thickness of the legs increases from the bar connecting the legs to the free end. The degree of the change in thickness also allows the bending of the leg to be influenced to a small extent, so that the bending of the leg can be adapted to the shape of the vertebral bodies if necessary.

The inner surfaces of the unbent legs can be flat.

It is beneficial if at least the supporting surfaces are structured. This fixes the supporting body between the vertebral bodies and this structuring can also help the bone material to grow into the supporting body.

For example, the structuring can be formed by spikes or tips protruding from the support surfaces or by recesses machined into the support surfaces. These can be designed as holes or slots, for example.

It is particularly advantageous if the structuring is formed by a porous coating of the support surfaces, which can at the same time be a particularly bone-friendly surface, so that the bone material grows into this surface.

Preferably, the support body is cuboid-shaped in the undeformed state.

In a special embodiment, it can be provided that the support body on its web side, seen from above,

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is shortened on one side by a bevel or by a curve. This makes it possible to accommodate longer support bodies in the space between two vertebrae without the support body protruding beyond the cross-section of the roughly circular vertebral body with a corner. The increase in the support surface leads to lower surface pressures and thus to a lower risk of the support body sinking into the bone material.

The following description of preferred embodiments of the invention serves to explain it in more detail in conjunction with the drawing. They show:

Figure 1: a cross-sectional view of a spine in the area between two vertebral bodies with two inserted intervertebral implants;

Figure 2: a longitudinal section through a spine in the area between two vertebral bodies with an inserted intervertebral implant and

Figure 3: a perspective view of an intervertebral implant.

The intervertebral implant of the present invention comprises a substantially U-shaped support body 1 with a cuboidal cross-section. In this support body 1 an interior space 2 with a trapezoidal cross-section is recessed,

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so that the support body 1 has two legs 3 and 4 running essentially parallel to one another and a web 5 running essentially perpendicularly thereto and connecting the two legs 3 and 4. Due to the trapezoidal cross section of the interior 2, the flat inner surfaces 6, 7 of the legs 3, 4 are inclined towards one another in such a way that they approach one another towards the free ends of the legs 3, 4. In addition, the thickness of the legs 3, 4 increases from the web 5 to the free ends of the legs 3, 4.

In the web 5 there is a continuous threaded hole 8, into which a screw 9 is screwed, which has a thread-free contact surface 10 in the form of a truncated cone at its free end. This rests in the front third on the two inner surfaces 6, 7 and expands the interior 2 more or less depending on the screw depth, i.e. the legs 3, 4 are elastically bent outwards under the influence of the screw 9. The screw 9 can be screwed in, for example, with a polygonal wrench 11, which is inserted into a polygonal opening in the screw (not shown in the drawing).

The outer surfaces of the legs 3, 4 form support surfaces 12, which are essentially flat when the support body 1 is undeformed and which curve slightly outwards when the screw 9 is screwed into the support body 1. These support surfaces 12, 13 can be provided with a structure in a way that is not apparent from the drawing, for example, tips or spikes can be placed there or holes can be drilled into the support surface 12, 13. This structuring improves the contact with the

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Support surface 12 adjacent bone tissue. In another embodiment, the support surfaces 12, 13 and possibly the entire support body 1 are coated with a rough surface, for example with a microporous surface, so that on the one hand the roughness can be increased and on the other hand the engagement with adjacent bone tissue can be improved.

The support body 1 and the screw 3 are made of biocompatible metals, metal alloys or plastics, for example titanium.

As can be seen from the representations in Figures 1 and 2, the support body 1 is inserted between two adjacent vertebral bodies 14 in such a way that the support surfaces 12 and 13 lie flat against the adjacent vertebral bodies. The support bodies 1 are always inserted in pairs between two vertebral bodies, the webs 5 are oriented in a dorsal direction, the free ends of the legs 3 and 4 in a ventral direction. In this way it is possible to screw the screw 9 into the support body 1 from the back to a greater or lesser depth in order to bend the legs 3, 4 and thus change the distance and possibly also, to a small extent, the mutual orientation of the adjacent vertebral bodies 14. With the simplest structure of the support body 1, the necessary support functions can be taken over by it. It is particularly advantageous that the intervertebral implant can also be removed again in a simple manner. It is sufficient to unscrew the screw 9 until the legs return to their undeformed position, then the support bodies 1 can be easily removed and replaced if necessary.

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While the support body described so far has cuboid-shaped outer contours, it is possible to deviate slightly from this. For example, the cuboid-shaped support body 1 in the area of the web 5 can have a cross-section that is beveled at one corner or shortened by an arc when viewed from above, as shown by the dashed boundary line 15 in Figure 1. A support body 1 modified in this way is adapted to the outer contour of the vertebral body 14 and can therefore be made correspondingly longer without protruding beyond the contour of the vertebral body 14. Since the intervertebral implants described are constructed completely symmetrically to a horizontal plane, it is sufficient to insert the support body 1, which is beveled laterally in this way or has an arc-shaped contour 15, in a different orientation, so that on one side the left corner and on the other side the right corner of the support body are shorter, as shown in Figure 1.

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Claims (1)

PROTECTION CLAIMS Intervertebral implant with support surfaces that can be placed on adjacent vertebral bodies and with an adjustment device for changing the relative position of the support surfaces, characterized in that the support surfaces (12, 13) are formed by the outer sides of the legs (3, 4) of a U-shaped support body (1) which run essentially parallel to one another, that a threaded bore (8) is arranged in a web (5) of the support body (1) which connects the legs (3, 4) to one another in one piece, and that a screw (9) is screwed into this, which rests on the inner surfaces (6, 7) of the legs (3, 4) which approach one another towards the free end of the legs (3, 4) and thereby bends the legs (3, 4) outwards more or less depending on their screw-in depth. Implant according to claim 1, characterized in that the screw (9) tapers conically in its tip region (10). AESCULAP AG J ; _# * &idigr;_#&idigr;_###&iacgr; * "iÄ*"#1969 U 9 May 1994 u-214 - 11 - 3. Implant according to claim 1 or 2, characterized in that the screw (9) is designed to be thread-free in its tip region (10). 4. Implant according to one of the preceding claims, characterized in that the screw (9) rests in the front third of the legs (3, 4) on their inner surface (6, 7). 5. Implant according to one of the preceding claims, characterized in that the thickness of the legs (3, 4) increases from the web (5) connecting the legs (3, 4) towards the free end. 6. Implant according to claim 5, characterized in that the inner surfaces (6, 7) of the unbent legs (3, 4) are flat. 7. Implant according to one of the preceding claims, characterized in that at least the support surfaces (12, 13) are structured. 8. Implant according to claim 7, characterized in that the structuring is formed by spikes or tips protruding from the support surfaces (12, 13). AESCULAP AG II ' III * **^?·&1969 u 9 May 1994 u-214 - 12 - 9. Implant according to claim 7, characterized in that the structuring is formed by recesses or openings worked into the support surfaces (12, 13). 10. Implant according to claim 7, characterized in that an additional structuring is formed by a coating of the support surfaces (12, 13). 11. Implant according to one of the preceding claims, characterized in that the support body (1) is cuboid-shaped in the undeformed state. 12. Implant according to claim 11, characterized in that the support body (1) is shortened on one side by a bevel or by a curve (15) on its web side when viewed from above.